N55 335i- A good BMW engine or a Source of Headache?

An Overview of the N55 335i

The N55 is a 3.0 liter, straight-six engine, which makes use of dual overhead cams, variable valve lift, and variable valve timing. Its power ranges anywhere from 302 horsepower to 365 horses, depending on which model you purchase. It's also turbocharged, to give the engine that extra kick of power.

The N55 has been used in a number of cars. Here are a few of the most popular models:

• BMW 135i
• BMW 535i
• BMW X5
• BMW M235i

So, the N55 is far from a ground-breaking engine. But BMW never intended it to be. The purpose of the N55 was to build on the N54 and provide the company with a reliable, powerful, and versatile engine to put in a variety of new models. It's certainly fulfilled its requirements and has some great features for the everyday driver.

Best features of the N55 335i

The N55 has some great features. Here are some of the best:

• Reliability:Whilst it's not the most reliable engine on the market, the N55 is much more reliable than its predecessor. This is due to superior build quality. For instance, the N55 saw a shift to a single turbocharger, which has proven more reliable than the previous twin-turbo setup. Furthermore, the N54 was seen as more of an experiment, whereas the N55 was the true final product. So, if you're looking for a reliable BMW engine, the N55 is a great choice, and you should certainly consider the N55 over the N54.
• Fuel Economy:Again, compared to the best engines on the market, the N55 certainly isn't the most fuel-efficient engine. However, it will average around 30mpg, which is very respectable for an engine that's 10 years old. Motorway driving is particularly efficient with the N55.
• Tuning capability:If you like to remap engines to get the most out of them, then the N55 is a great choice. It's a very easy engine to tune and has some great potential. For instance, an ethanol tune can give the N55 more than 450 horses.

Common Problems with the N55 335i

Whilst the N55 335i has some excellent qualities, it's certainly not a perfect engine. Here are some of the N55 335i's biggest flaws:

1. Valve Cover Oil Leak

This is perhaps one of the most common, yet annoying, problems with the N55 335i. The valve cover gasket is made of rubber, which over time, degrades due to exposure to high temperatures. Eventually, the gasket will crack, which can result in oil leaks and even a build-up of oil within your engine. The same is true for the oil valve cover. It's made of plastic and will quickly crack when exposed to high temperatures. Whilst the repercussions won't be as serious as the gasket cracking, it can still damage your engine, and if you purchase an N55 335i, you should consider replacing both the valve cover gasket and the valve cover as soon as possible.

If you're worried that your gasket or valve cover has cracked and is now leaking oil, there are a few symptoms to be aware of. For instance, check to see if your oil warning light is low and be aware of smoke or a burning smell from the engine.

Replacing the valve cover and gasket is actually pretty simple and could save you a great deal of money in the long run. It's a difficult job to do yourself, so you should only attempt to replace these parts if you're experienced in car DIY.

2. Water Pump Failure

Another problem with the N55 335i, and BMW engines in general, is that the water pump is prone to failure. This can be a major problem, as an engine's water pump is responsible for cooling the engine, and if it breaks, the engine can overheat quickly. The problem with the N55's water pump is that it uses electric pumps powered by a composite impeller, which are notoriously unreliable. In fact, some drivers have reported water pump failure at as early as 52,000 miles, showing just how unreliable the water pump is.

Unfortunately, there are no symptoms of a faulty water pump. Water pumps tend to brake suddenly and without warning, so it can be hard to diagnose the problem before it happens. That being said, if your engine starts to overheat, or your fan makes a continuous loud noise, you should check your water pump as these are good signs that it's malfunctioned.

Replacing a water pump can set you back $1,000 or more. Although, installation is pretty simple and installing a new pump yourself could save you around $500.

3. Faulty oil Filter Housing Gasket

Another major problem with the N55 335i engine is that the oil filter housing gasket is poorly made, and prone to leaking over time. Whilst this isn't a major problem in itself, it can cause oil to leak onto the drive belt, which can cause the belt to snap or even slip from its mount. This in turn can cause serious damage to the engine, particularly if the crankshaft is damaged. This would rarely happen, but it does show that poor quality even in smaller parts of an engine can lead to bigger problems in the long run.

Luckily, the oil filter housing gasket is incredibly cheap to replace. In fact, you can buy a replacement for less than $20, and its fairly easy installation means you can save hundreds on labor costs too. Considering the price, it's a good idea to replace the oil filter housing gasket, as it may save you a lot of money down the line.

4. Variable Camshaft Timing Failure

More commonly referred to as VANOS, the N55's variable camshaft timing regulates the timing of intake and exhaust camshafts, to provide a smooth ride and increase fuel economy. The VANOS is one of the hardest working components in the engine, making it suspectable to wear and damage over time. Furthermore, the solenoids can become covered in oil, which can lead to several problems.

There are a few symptoms to suggest your VANOS solenoids have failed. For instance, you'll be able to notice a loss of power, a greater chance of stalling, a more uncomfortable ride, and your car going into 'limp mode'.

A BMW N55 335i engine has two solenoids, which cost around $160 each. Factor in labor costs and a faulty VANOS system can be expensive to repair. If you're fairly experienced in DIY, you might be able to fit these yourself, but if you're a beginner, we don't recommend this.

5. High Pressure Fuel Pump Failure

The final problem with the N55 engine is that the high-pressure fuel pump is susceptible to damage and subsequent failure. This has widely been renowned as one of the engine's most common problems, and the company only found an effective solution in 2011. So, if you have an N55 engine produced before this date, you may want to have the fuel pump checked out.

Is the N55 a good engine?

So, is the BMW N55 335i engine a good choice, or should you avoid it at all costs?

Despite the vast list of common problems, the N55 is actually a very reliable engine. It's much more reliable than its predecessor, and you'll most likely only start to encounter problems with the engine at around 100,000 miles. So, if you're looking for a workhorse, the N55 is far from a poor choice.

The N55 is also fun to drive, thanks to its solid power output. In most vehicles, you won't feel like you need more power, and the turbocharger makes the N55 even more enjoyable. Many people loved the N54 for its entertainment factor, and the N55 builds on this even further.

As for fuel economy, the N55 can't keep up with more modern engines, but that isn't to say it will burn through fuel. The N55 is incredibly economical on motorways, and you'd be surprised at its everyday fuel efficiency.

Final words

Perhaps the biggest problem with the N55 is that it's been superseded by the B58 engine. This is because of new emission regulations, which the N55 will struggle to pass. As long as you don't tamper with the DPF, it may be able to scrape by, but in a few years, it will certainly fall off. This might just make the N55 unusable in the near future, making it an overall poor choice.

Ultimately, the N55 is a solid and reliable engine, but the fact that it won't be able to keep up with new emission regulations makes it a poor choice in today's market.